Fluids

These days, drinking fluids during exercise is considered normal behavior. The importance of drinking water was first documented during the construction of the Hoover Dam near Las Vegas in the mid-1930's. Unfortunately, the athletic community didn't catch on until the middle 1960's. In the late 60's and early 70's, the opinion of many began to shift and drinking water during exercise started to become commonplace. Nowadays, withholding water might even be considered negligent.

We begin to sweat within the first seconds of exercise, but we don't perceive it on our skin because the sweat evaporates so fast. Once our body temperature rises, sweat production exceeds evaporation and that is when we start to notice it on our skin. Evaporation of the sweat is the actual loss of heat. The lower the humidity, the faster the evaporation. There are even modern fabrics that help in the evaporation process. Sweat is mostly water. The amount of salt in sweat is small, so our most important task is to replace water. (were you aware that the first sports drink, Gookin-Aid, was simply the salt and water composition of the sweat of a runner named Matt Gookin?) We don't begin to get thirsty until about 1% of our body weight is lost. However, our thirst mechanism is not very good.

We get thirsty after we've started to become dehydrated. When we start drinking, we satisfy our thirst before we have replaced the lost fluid. If we lose 3 pounds of weight by sweating (that is 3 pints of water-remember that relationship: 1 pint of water = 1 pound of body weight), we don't drink back those 3 pints of lost water. We typically stop drinking well before full replacement of water. It is best to drink some fluids 15-20 minutes prior to exercise. Two to three good size mouthfuls of fluid is about right. Drink 2-3 mouthfuls every 15-20 minutes during exercise (performance drops off with dehydration not too mention that the real risk of heat illness accompanies dehydration) Drinking during exercise helps keep performance up and the body temperature from getting too high. Place water bottles around the field, in the goals, and make it easily accessible on the bench so players can freely drink during the game. Use the normal stoppages in play to replenish your fluids-remember, a 90-minute game only has around 60 minutes of play, even less on hotter days so there are plenty of opportunities to drink. Water or a commercial drink? Actually, the salt in the commercial drinks helps get the water absorbed a little faster. Taste also has a lot to do with it. The better the taste (water is a bit bland) the more consumed. Carbonated sodas are never a good choice -- not before, during or after a game. The carbonation fills you up too fast and you drink less. It takes a while to replenish your fluid levels. Do not force fluids in a short period of time. Research shows that it can take up to 6 hours to get back to a normal water balance. To get back into water balance after exercise, drink 1.5 times your weight loss.

Therefore, if you lose 4 lbs. of weight in a game (4 pints of water) - you should drink 6 pints of fluids in the hours after the game. Remember to drink 8 glasses of water (or 2 of those 32 oz water bottles many players have) every day. The suggestions mentioned are in addition to the normal 8 glasses per day.

Heat illness is a very dangerous condition, but it is an entirely preventable problem. Drink before, during and after each exercise session. Weigh yourself at the same time each day. Unless you are trying to lose weight, your weight should be stable. If it's not, you may be becoming progressively dehydrated.

This sports science article comes from the Sports Medicine Section at the Duke University Medical Center and UNC Hospitals. The authors are members of the US Soccer Sports Medicine Committee including from UNC Dr. William E. Garrett, Jr (US National Teams Physician and Committee Chairman), and John Lohnes. From Duke are Dr. Don Kirkendall (exercise physiologist) and Patty Marchak (athletic trainer for 1996 US Women's Olympic Team).

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